OBJECTIVES: I. Compare the overall response rate and overall survival of patients with recurrent metastatic colorectal adenocarcinoma treated with third-line therapy comprising fluorouracil and leucovorin calcium with or without oxaliplatin. II. Compare the onset and duration of complete and partial responses and duration of disease stabilization in patients treated with these regimens. III. Compare the proportion of patients with stable disease and proportion of patients with tumor-related symptomatic improvement treated with these regimens. IV. Compare the time to disease progression and time to tumor-related symptomatic worsening in patients treated with these regimens.